This trial will be a Phase II, randomized, partially-blinded study evaluating the safety and efficacy of HU when added to potent antiretroviral therapy in subjects with plasma HIV RNA already suppressed below the level of detection. The primary endpoints of the study will be loss of viral suppression (HIV RNA > 200 copies/mL) or study drug toxicity. 399 HIV+ subjects will be enrolled in the study. HIV-infected subjects with documented plasma HIV RNA < 200 copies/ml after having received at least 6 months of IDV, ZDV and 3TC. ACTG 343 subjects must currently have a CD4 count >200 cells/mm(3) and must have had a documented CD4 count >100 cells/mm(3) within the 3 months prior to beginning their IDV/ZDV/3TC regimen. Subjects must not have any contraindication to ddI, d4T or HU or have had any exposure to protease inhibitors other than indinavir. Subjects will be stratified by participation.